The formation of dye images in most silver halide color photographic materials depends on the reduction of exposed silver halide grains with an aromatic primary amine color developing agent and the subsequent coupling of the resultant oxidation product of the color developing agent with couplers that respectively form yellow, magenta and cyan dyes.
Pyrazolone type couplers are commercially used as couplers for providing magenta dyes, but they have an unwanted secondary absorption and their keeping quality, particularly their resistance to formalin gas, is relatively low.
A variety of 1-H-pyrazolo[3,2-c]-S-triazole derived magenta couplers have been proposed to overcome these problems of the conventional pyrazoline type couplers. Reference should be had to U.S. Pat. No. 3,725,067, as well as British Pat. Nos. 1,252,418 and 1,334,515. The compounds disclosed in these patents avoid the problem of secondary absorption but the improvement is inadequate in terms of resistance to formalin gas and is insignificant in respect of the production of a light-fast magnenta dye image. The compound disclosed in Research Disclosure No. 12443 has no commercial value because of its low color formation. The 1H-pyrazolo[3,2-c]-S-triazole type magneta coupler disclosed in Unexamined Published Japanese Patent Application No. 42045/1983 features significant improvements in formalin resistance and color formation but little improvement has been achieved in terms of the production of a light-fast image.
Improved color development has also been achieved by the couplers described in Unexamined Published Japanese Patent Application Nos. 99437/1984 and 125732/1984 but the dye images produced by these couplers are still low in light fastness. The coupler disclosed in Unexamined Published Japanese Patent Application No. 99437/1984 depends on the concomitant use of additives for providing a light-fast image. The coupler disclosed as Compound No. 19 in Unexamined Published Japanese Patent Application No. 125732/1984 produces a dye image having slightly improved light fastness but the improvement is far from being satisfactory.
In short, the 1-H-pyrazolo[3,2-c]-S-triazole derived magenta couplers that have been considered useful because of the absence of secondary absorption and their high resistance to formalin gas fall far short of satisfying the requirement for providing dye images with improved light fastness.